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This GIS dataset is reproduced from: “Best, M.G., Lemmon, D.M., and Morris, H.T., 1989, Geologic map of the Milford quadrangle and east half of the Frisco quadrangle, Beaver County, Utah: U.S Geological Survey Miscellaneous Investigations Series Map I-1904, 1 plate, scale 1:50,000.” The map covers six standard 7.5' quadrangles in southwestern Utah: Frisco, Milford NW, Milford, Milford Flat, Picacho Peak, and White Mountain, and a narrow strip of the eastern portions of Frisco SW and Wallaces Peak. The GIS dataset was completed by Andrew Lawrence, Dustin Joe, Patrick Lowe, Lawrence Kellum, and Kade Carlson, students at Utah Valley University, and final GIS review and preparation for public release were completed by Zach Anderson, a geologist with the Utah Geological Survey.The UGS appreciates the volunteered time and effort of Utah Valley University students Andrew Lawrence, Dustin Joe, Patrick Lowe, Lawrence Kellum, and Kade Carlson who produced the GIS data for this project under the guidance of Utah Valley University professor Suzanne Walther.The southern Milford-Frisco area is in the Basin and Range Province of southwestern Utah and is dominated by north-south-trending mountain ranges and broad valleys. The prominent ranges in this map area are the San Francisco Mountains, Beaver Lake Mountains, Rocky Range, Star Range, and the Shauntie Hills. On the west side of the map, the Wah Wah Valley bounds the west side of the San Francisco Mountains and Shauntie Hills. On the east side of the map, the Escalante desert bounds the east side of the Beaver Lake Mountains, Rocky Range, and Star Range. In the Star Range, Lower Devonian through Lower Jurassic sedimentary rocks are thrust over Triassic and Jurassic rocks by the Blue Mountain thrust. In the Shauntie Hills, the Blue Mountain thrust is not exposed but the Devonian and Mississippian rocks that crop out within the range are likely part of the upper plate of the fault. In the southern part of the San Francisco Mountains, a thrust fault places Late Cambrian through Middle Ordovician rocks over Permian and Pennsylvanian rocks. This thrust fault is likely the Blue Mountain thrust; however, exposures of the fault are not continuous between ranges so correlation of these faults is speculative. In the Rocky Range, undifferentiated Paleozoic rocks are thrust over Permian rocks. The thrust faulting within the map area is a result of contractional deformation that occurred during the Cretaceous Sevier orogeny. The numerous east-west-striking faults in the Star Range likely accompanied and accommodated thrust faulting. Oligocene to Miocene volcanic, intrusive, and volcaniclastic rocks unconformably overlie and intrude Paleozoic and Mesozoic rocks. Iron and copper mineralization are associated with emplacement of the larger bodies of intrusive rock. Dominantly north- to northeast-striking normal faults cut Paleozoic-Cenozoic rocks and are the result of Tertiary Basin and Range extension. A zone of east-striking normal faults cuts the south-central part of the Shauntie Hills and southern part of the Star Range. A large Tertiary normal fault bounds the east side of Wah Wah Valley. Smaller faults near Copper Gulch, likely related to the range-bounding fault, cut Quaternary alluvium. This dataset was produced as part of a UGS multi-decade effort to provide statewide intermediate-scale (approximately 1:50,000 to 1:100,000) GIS data to the public, federal to local government agencies, educational groups, exploration and development companies, and other map users. The GIS dataset reproduces the original source map as close as reasonably possible; however, some geologic decisions were made to resolve cartographic problems such as inconsistent faults and incomplete polygons. We changed some geologic line symbols to better match the UGS 2018 data model. While the map is considered a good representation of the geology of the map area, users should be aware that it was produced in 1989 and does not meet all modern cartographic, spatial control, or geologic standards. Line and point attributes and symbology were selected from current (2018) UGS schema and do not necessarily match the intent of the original map. Selected attributes most closely represent the general geologic interpretation depicted on the original map, but are not an exact match, as noted below. ContactsOriginal attribute is “Contact – Dashed where approximately located; some Quaternary contacts shown as solid are approximately located.” These lines are now depicted as “Contact, well located”; “Contact, approximately located”; or “Contact, concealed.”Normal FaultsOriginal attribute is “High-angle fault – Dashed where approximately located; dotted where concealed; groups of three dots where inferred and concealed; bar and ball on downthrown side”. These lines are now depicted as “Fault, normal, well located”; “Fault, normal, approximately located”; or “Fault, normal, concealed.”Geophysical FaultsOriginal attribute is “High-angle fault – Dashed where approximately located; dotted where concealed; groups of three dots where inferred and concealed; bar and ball on downthrown side.” These lines are now depicted as “Fault, geophysical, gravity.”Strike-slip FaultsLine types do not have a description in the explanation of the original map. These lines are now depicted as “Fault, strike-slip, right-lateral, well located”; “Fault, strike-slip, right-lateral, approximately located”; “Fault, strike-slip, left-lateral, well located”; or “Fault, strike-slip, left-lateral, concealed.”Thrust FaultsOriginal attribute is “Thrust fault – Dotted where concealed; sawteeth on upper plate.” These lines are now depicted as “Fault, thrust, type 1, well located” or “Fault, thrust, type 1, concealed.”General FaultsLine types do not have a description in the explanation of the original map. These lines are now depicted as “Fault, unknown, well located”; “Fault, unknown, approximately located”; or “Fault, unknown, concealed.”FoliationOriginal attribute is “Strike and dip of compaction foliation in welded tuffs.” These points are now depicted as “Foliation, inclined, field measured.” Units – Descriptions/Names/AgesMap is not modified from original source map even in locations where newer interpretations may exist. |